Chemical generation systems and methods often involve complex equipment and abundant energy sources to produce the quantity, quality and concentration of the chemical. Such generators are often expensive and bulky so that the end-user must rely on a commercial generation source to produce the chemical needed which involves both transportation and storage costs and concerns. In the case of sensitive chemicals, such as chlorine dioxide, commercial generation is not usually an acceptable solution for consumers. Chlorine dioxide is a widely used sanitizer in a number of fields such as food processing and water treatment. Some recent approvals by the Food and Drug Administration have made chlorine dioxide a popular choice for sanitizing fruits, vegetables, and seafood. Since chlorine dioxide gas is explosive in nature and cannot be safely transported, it should be generated on-site.
A common method for the generation of chlorine dioxide is the acidification of chlorite or chlorate salts. In food related uses, chlorite salts prevail because of their ability to break down into non toxic by-products. Among acids, any food grade acid, including phosphoric, hydrochloric or citric acid, can be used for this purpose.
Chlorine dioxide generation is most efficient when the precursors are mixed as concentrates. The optimum pH for the reaction is between 2 and 3. At pH values higher than 3, the reaction is not very efficient. On the other hand, at pH values lower than 2, unwanted by-products may be formed. Typically, a 1 to 5 percent chlorite solution is mixed with a selected acid to generate chlorine dioxide. Mixing of the acid with the precursor (chlorite or chlorate) ion is referred as “activation.” The time between mixing of the precursors and dilution of the activated mixture is known as the “activation time.” To achieve good efficiency of chlorine dioxide generation, 1 to 10 minutes of activation time is usually recommended. This is the time that must lapse before the concentrate is diluted to the target usage concentration. For most sanitary and odor removal applications, the usage concentration typically falls between 1 to 600 ppm of activated product so the product is usually diluted to a concentration within this range. As an alternative to dilution, the concentrate can be metered directly into a flowing water stream; or a batch of concentrate can be dumped directly into a larger water system, such as a vegetable flume, a water storage vessel or a cooling tower, to attain and maintain the proper level of chlorine dioxide concentration.
Mixing of precursors for the production of chlorine dioxide can be accomplished using automated systems. There are several commercial companies that manufacture acid/sodium chlorite generators, such as Belazon Incorporated and Alldos Corporation. However, all commercially available generators known to the marketplace are electrically powered, and all such commercially available generators utilize high cost electronic control logic.
There is a need for a chemical generator that is non-electric, can be installed to operate in remote locations where electrical power is unavailable, can store a reasonable supply of the generated chemical, and is inexpensive to manufacture and maintain.